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• Help me find article on Multi-threading and Event Handling in Java

  - by JDR

  I once read an article on how to properly write event handlers for multi-threading in Java, but I can't for the life of me find it anymore. It described the pitfalls and potentials for deadlocks that can occur when firing events (not Swing events mind you, but general events like model update notifications). To clarify, the situation would be as such: // let's say this is code from an MVC model somewhere public void setSomeProperty(String myProperty){ if(!this.myProperty.equals(myProperty)){ this.myProperty = myProperty; fireMyPropertyChangedEvent(...); } } The article described how passing control to arbitrary external listener code was a potential cause for deadlock. I now find myself in a situation where I need to fire such events in a multithreaded environment and I would very much like to read the article again to see what it has to say before I continue. Does anyone know the article I'm referring to? I believe it came as a (fairly short) PDF. It started off with an initial naive implementation and incrementally pointed out flaws and improved upon it. It ended with a sort of final proper-way-to-fire-multithreaded-events. I've searched endlessly in my browse history and on google, but all I could find were endless amounts topics on Swing event dispatch threads. Thank you.

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• Rapid Opening and Closing System.IO.StreamWriter in C#

  - by ccomet

  Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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• NSMutableArray for Object which has NSString property causes memory leak

  - by user262325

  Hello everyone I hope to add objects to a NSMutableArray "myArray", The NSMutableArray is the array for FileObj which has a NSString property "fileName" #import <UIKit/UIKit.h> @interface FileObj : NSObject { NSString *fileName; } -(void) setfileName:(NSString *)s ; -(NSString *) getfileName ; @end // // File.m// #import "File.h" @implementation FileObj -(void) setfileName:(NSString *)s ; { fileName=s; } -(NSString *) getfileName ; { return fileName; } @end I initialize the myArray here: NSMutableArray *temarray; temarray=[[NSMutableArray alloc] init]; self.myArray=temarray; [temarray release]; the codes to add object to myArray FileObj *newobj=[[FileObj alloc]init ]; NSString *fieldValue2 = [[NSString alloc] initWithUTF8String:@"aaaa"]; [newobj setfileName:fieldValue2]; [myArray addObject:newobj]; [fieldValue2 release]; //**if I enabled the line, it will cause crash** //**if I disable the line, it will cause memory leak** [newobj release]; Welcome any comment Thanks interdev

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• Java Detect Variable Change Using PropertyChangeSupport and PropertyChangeListener

  - by Sam

  I'm trying to print out debug statements when some third party code changes a variable. For example, consider the following: public final class MysteryClass { private int secretCounter; public synchronized int getCounter() { return secretCounter; } public synchronized void incrementCounter() { secretCounter++; } } public class MyClass { public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // add code here to detect calls to incrementCounter and print a debug message } I don't have the ability to change the 3rd party MysteryClass, so I thought that I could use PropertyChangeSupport and PropertyChangeListener to detect changes to the secretCounter: public class MyClass implements PropertyChangeListener { private PropertyChangeSupport propertySupport = new PropertyChangeSupport(this); public MyClass() { propertySupport.addPropertyChangeListener(this); } public void propertyChange(PropertyChangeEvent evt) { System.out.println("property changing: " + evt.getPropertyName()); } public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // do logic which involves increment and getting the value of MysteryClass } } Unfortunately, this did not work and I have no debug messages printed out. Does anyone see what is wrong with my implementation of the PropertyChangeSupport and Listener interfaces? I want to print a debug statement whenever incrementCounter is called or the value of secretCounter changes.

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• MVC design pattern in complex iPad app: is one fat controller acceptable?

  - by nutsmuggler

  I am building a complex iPad application; think of it as a scrapbook. For the purpose of this question, let's consider a page with two images over it. My main view displays my doc data rendered as a single UIImage; this because I need to do some global manipulation over them. This is my DisplayView. When editing I need to instantiate an EditorView with my two images as subviews; this way I can interact with a single image, (rotate it, scale it, move it). When editing is triggered, I hide my DisplayView and show my EditorView. In a iPhone app, I'd associate each main view (that is, a view filling the screen) to a view controller. The problem is here there is just one view controller; I've considered passing the EditorView via a modal view controller, but it's not an option (there a complex layout with a mask covering everything and palettes over it; rebuilding it in the EditorView would create duplicate code). Presently the EditorView incorporates some logic (loads data from the model, invokes some subviews for fine editing, saves data back to the model); EditorView subviews also incorporate some logic (I manipulate images and pass them back to the main EditorView). I feel this logic belongs more to a controller. On the other hand, I am not sure making my only view controller so fat a good idea. What is the best, cocoa-ish implementation of such a class structure? Feel free to ask for clarifications. Cheers.

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• Mono Develop 2.4.1 + linq error.

  - by Nev_Rahd

  I just started to learn Mono Develop Installed Mono Develop 2.4.1 and trial version of Mono Touch. my Code: using System; using System.Xml.Linq; using System.Collections.Generic; namespace RSSReader { public static class RSSRepository { public static IList<FeedItem> GetFeeds(string url) { XDocument rssFeed = XDocument.Load(url); Console.Write(rssFeed.ToString()); var feeds = new List<FeedItem>(); try { var query = from item in rssFeed.Descendants("item") select new FeedItem { Title = item.Element("title").Value, Published = DateTime.Parse(item.Element("pubDate").Value), Url = item.Element("link").Value }; feeds = query.ToList(); } catch (Exception ex){ Console.WriteLine(ex.Message); } return feeds; } } } This is throwing an error: An implementation of 'select' query expression pattern could not be found. Are you missing 'System.linq' using directive or 'System.Core.dll' assembly reference? I got both references to System.Xml.Linq and System.Core What am i missing ?

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• Need help/guidance about creating a desktop application with gui

  - by Somebody still uses you MS-DOS

  I'm planning to do an Desktop application using Python, to learn some Desktop concepts. I'm going to use GTK or Qt, I still haven't decided which one. Fact is: I would like to create an application with the possibility to be called from command line, AND using a GUI. So it would be useful for cmd fans, and GUI users as well. It would be interesting to create a web interface too in the future, so it could be run in a server somewhere using an html interface created with a template language. I'm thinking about two approaches: - Creating a "model" with a simple interface which is called from a desktop/web implementation; - Creating a "model" with an html interface, and embeb a browser component so I could reuse all the code in both desktop/web scenarios. My question is: which exactly concepts are involved in this project? What advantages/disadvantages each approach has? Are they possible? By naming "interface", I'm planning to just do some interfaces.py files with def calls. Is this a bad approach? I would like to know some book recommendations, or resources to both options - or source code from projects which share the same GUI/cmd/web goals I'm after. Thanks in advance!

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• crash when using stl vector at instead of operator[]

  - by Jamie Cook

  I have a method as follows (from a class than implements TBB task interface - not currently multithreading though) My problem is that two ways of accessing a vector are causing quite different behaviour - one works and the other causes the entire program to bomb out quite spectacularly (this is a plugin and normally a crash will be caught by the host - but this one takes out the host program as well! As I said quite spectacular) void PtBranchAndBoundIterationOriginRunner::runOrigin(int origin, int time) const // NOTE: const method { BOOST_FOREACH(int accessMode, m_props->GetAccessModes()) { // get a const reference to appropriate vector from member variable // map<int, vector<double>> m_rowTotalsByAccessMode; const vector<double>& rowTotalsForAccessMode = m_rowTotalsByAccessMode.find(accessMode)->second; if (origin != 129) continue; // Additional debug constrain: I know that the vector only has one non-zero element at index 129 m_job->Write("size: " + ToString(rowTotalsForAccessMode.size())); try { // check for early return... i.e. nothing to do for this origin if (!rowTotalsForAccessMode[origin]) continue; // <- this works if (!rowTotalsForAccessMode.at(origin)) continue; // <- this crashes } catch (...) { m_job->Write("Caught an exception"); // but its not an exception } // do some other stuff } } I hate not putting in well defined questions but at the moment my best phrasing is : "WTF?" I'm compiling this with Intel C++ 11.0.074 [IA-32] using Microsoft (R) Visual Studio Version 9.0.21022.8 and my implementation of vector has const_reference operator[](size_type _Pos) const { // subscript nonmutable sequence #if _HAS_ITERATOR_DEBUGGING if (size() <= _Pos) { _DEBUG_ERROR("vector subscript out of range"); _SCL_SECURE_OUT_OF_RANGE; } #endif /* _HAS_ITERATOR_DEBUGGING */ _SCL_SECURE_VALIDATE_RANGE(_Pos < size()); return (*(_Myfirst + _Pos)); } (Iterator debugging is off - I'm pretty sure) and const_reference at(size_type _Pos) const { // subscript nonmutable sequence with checking if (size() <= _Pos) _Xran(); return (*(begin() + _Pos)); } So the only difference I can see is that at calls begin instead of simply using _Myfirst - but how could that possibly be causing such a huge difference in behaviour?

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• C++ std::vector memory/allocation

  - by aaa

  from a previous question about vector capacity, http://stackoverflow.com/questions/2663170/stdvector-capacity-after-copying, Mr. Bailey said: In current C++ you are guaranteed that no reallocation occurs after a call to reserve until an insertion would take the size beyond the value of the previous call to reserve. Before a call to reserve, or after a call to reserve when the size is between the value of the previous call to reserve and the capacity the implementation is allowed to reallocate early if it so chooses. So, if I understand correctly, in order to assure that no relocation happens until capacity is exceeded, I must do reserve twice? can you please clarify it? I am using vector as a memory stack like this: std::vector<double> memory; memory.reserve(size); memory.insert(memory.end(), matrix.data().begin(), matrix.data().end()); // smaller than size size_t offset = memory.size(); memory.resize(memory.capacity(), 0); I need to guarantee that relocation does not happen in the above. thank you. ps: I would also like to know if there is a better way to manage memory stack in similar manner other than vector

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• MEF: Satisfy part on an Export using and Export from the composed part.

  - by Pop Catalin

  Hi, I have the following scenario in Silverlight 4: I have a notifications service Snippet [InheritedExport] public interface INotificationsService : IObservable<ReceivedNotification> { void IssueNotifications(IEnumerable<ClientIssuedNotification> notifications); } and and implementation of this service Snippet [PartCreationPolicy(CreationPolicy.NonShared)] public class ClientNotificationService : INotificationsService { [Import] IPlugin Plugin { get; set; } ... } How can I say to MEF that the Plugin property of the ClientNotificationService must be provided by the importing class that imports the INotificationsService. For example: Snippet public class Client { [Export] IPlugin Current { get; set; } [Import] INotificationService NotificationService; } How can I say that I want MEF to satisfy the ClientNotificationService.Plugin part with the exported IPlugin by the Client class. Basically I want the NotificationService, to receive a Unique ID provided by the importing class, whenever it is created and composed to a new class, or if there's and alternative method, like using meta data to do this I'd appreciate any insights. I've been struggling with this for a while. Thanks

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• [PHP, CSS, & ?] fixed width div, resizing text on the fly based on length

  - by Andrew Heath

  Let's say you've got a simple fixed-width layout that pulls a title from a MySQL database. CSS: #wrapper { width: 800px; } h1 { width: 100%; } HTML: <html> <body> <div id="wrapper"> <h1> $titleString </h1> </div> </body> </html> But the catch is, the length of the title string pulled from your MySQL database varies wildly. Sometimes it might be 10 characters, sometimes it might be 80. It's possible to establish a min & max character count. How, if at all possible, do I get the text-size of my <h1>$titleString</h1> to enlarge/decrease on-the-fly such that the string is only ever on one line and best fit to that line length? I've seen a lot of questions about resizing the div - but in my case the div must always be 100% (800px) and I want to best-fit the title. Obviously a maximum text-size value would have to be set so 5 character strings don't become gargantuan. Does anyone have a suggestion? I'm only using PHP/MySQL/CSS on this page at the moment, but incorporation of another language is fine if it means I can solve the problem. The only thing I can think of is a bruteforce approach whereby through trial and error I establish acceptable string character count ranges matched with CSS em sizes, but that'd be a pretty ugly implementation from the code side.

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• Caching vector addition over changing collections

  - by DRMacIver

  I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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• How do I configure encodings (UTF-8) for code executed by Quartz scheduled Jobs in Spring framework

  - by Martin

  I wonder how to configure Quartz scheduled job threads to reflect proper encoding. Code which otherwise executes fine within Springframework injection loaded webapps (java) will get encoding issues when run in threads scheduled by quartz. Is there anyone who can help me out? All source is compiled using maven2 with source and file encodings configured as UTF-8. In the quartz threads any string will have encoding errors if outside ISO 8859-1 characters: Example config <bean name="jobDetail" class="org.springframework.scheduling.quartz.JobDetailBean"> <property name="jobClass" value="example.ExampleJob" /> </bean> <bean id="jobTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean"> <property name="jobDetail" ref="jobDetail" /> <property name="startDelay" value="1000" /> <property name="repeatCount" value="0" /> <property name="repeatInterval" value="1" /> </bean> <bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean"> <property name="triggers"> <list> <ref bean="jobTrigger"/> </list> </property> </bean> Example implementation public class ExampleJob extends QuartzJobBean { private Log log = LogFactory.getLog(ExampleJob.class); protected void executeInternal(JobExecutionContext ctx) throws JobExecutionException { log.info("ÅÄÖ"); log.info(Charset.defaultCharset()); } } Example output 2010-05-20 17:04:38,285 1342 INFO [QuartzScheduler_Worker-9] ExampleJob - vÖvÑvñ 2010-05-20 17:04:38,286 1343 INFO [QuartzScheduler_Worker-9] ExampleJob - UTF-8 The same lines of code executed within spring injected beans referenced by servlets in the web-container will output proper encoding. What is it that make Quartz threads encoding dependent?

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• How to provide warnings during validation in ASP.NET MVC?

  - by Alex

  Sometimes user input is not strictly invalid but can be considered problematic. For example: A user enters a long sentence in a single-line Name field. He probably should have used the Description field instead. A user enters a Name that is very similar to that of an existing entity. Perhaps he's inputting the same entity but didn't realize it already exists, or some concurrent user has just entered it. Some of these can easily be checked client-side, some require server-side checks. What's the best way, perhaps something similar to DataAnnotations validation, to provide warnings to the user in such cases? The key here is that the user has to be able to override the warning and still submit the form (or re-submit the form, depending on the implementation). The most viable solution that comes to mind is to create some attribute, similar to a CustomValidationAttribute, that may make an AJAX call and would display some warning text but doesn't affect the ModelState. The intended usage is this: [WarningOnFieldLength(MaxLength = 150)] [WarningOnPossibleDuplicate()] public string Name { get; set; } In the view: @Html.EditorFor(model => model.Name) @Html.WarningMessageFor(model => model.Name) @Html.ValidationMessageFor(model => model.Name) So, any ideas?

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• Mono Text Based Web Browser

  - by powerbox

  Hi guys, is there any public text based web browser implementation for C# or on mono base api that I can use to fill up web forms automatically? I'll be using it to automate some web task that does not require any image authentication. I'm currently using a web browser control available on .Net Framework and waits for the event WebBrowserDocumentCompletedEventHandler to fire after a page is successfully loaded and invoke some actions like Submit or simulating a mouse click on some links. It actually does the job but I can't process bulk transactions since I needed to wait for the whole page to be loaded together with the images and other stuff. It is easy to use HttpWebRequest to fill up some forms , provide some data and then submit. But on some occasions I only need to simulate a mouse click to a certain link which I don't know how to do with HttpWebRequest. By the way using HttpWebRequest will still download all the images of a web page that I see pointless since I only need to provide correct data back to the server. I hope someone can pinpoint me the correct way of doing this kind of automation and thanks in advance!

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• Using before_create in Rails to normalize a many to many table

  - by weotch

  I am working on a pretty standard tagging implementation for a table of recipes. There is a many to many relationship between recipes and tags so the tags table will be normalized. Here are my models: class Recipe < ActiveRecord::Base has_many :tag_joins, :as => :parent has_many :tags, :through => :tag_joins end class TagJoin < ActiveRecord::Base belongs_to :parent, :polymorphic => true belongs_to :tag, :counter_cache => :usage_count end class Tag < ActiveRecord::Base has_many :tag_joins, :as => :parent has_many :recipes, :through => :tag_joins, :source => :parent , :source_type => 'Recipe' before_create :normalizeTable def normalizeTable t = Tag.find_by_name(self.name) if (t) j = TagJoin.new j.parent_type = self.tag_joins.parent_type j.parent_id = self.tag_joins.parent_id j.tag_id = t.id return false end end end The last bit, the before_create callback, is what I'm trying to get working. My goal is if there is an attempt to create a new tag with the same name as one already in the table, only a single row in the join table is produced, using the existing row in tags. Currently the code dies with: undefined method `parent_type' for #<Class:0x102f5ce38> Any suggestions?

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• Intelligent search and generation of Java code, preferrably using Python?

  - by Ipsquiggle

  Basically, I do lots of one-off code generation, large-scale refactorings, etc. etc. in Java. My tool language of choice is Python, but I'll take whatever solutions you can offer. Here is a simplified illustration of what I would like, in a pseudocode Generating an implementation for an interface search within my project: for each Interface as iName: write class(name=iName+"Impl", implements=iName) search within the body of iName: for each Method as mName: write method(name=mName, body="// TODO implement this...") Basically, the tool I'm searching for would allow me to: parse files according to their Java structure ("search for interfaces") search for words contextualized by language elements and types ("variables of type SomeClass", "doStuff() method calls on SomeClass instances") to run searches with structural context ("within the body of the current result") easily replace or generate code (with helpers to generate, as above, or functions for replacing, "rename the interface to Foo", "insert the line Blah.Blah()", etc.) The point is, I don't want to spend a lot of time writing these things, as they are usually throwaway. But sometimes I need something just a little smarter than what grep offers. It wouldn't be too hard to write up a simplistic version of this, but if I'm going to use something like this at all, I'd expect it to be robust. Any suggestions of a tool/library that will help me accomplish this?

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• Undeclared - 'first use in function'

  - by Ragunath Jawahar

  I'm new to Objective-C, though I have a very good hand in Android. I'm trying to make a call to a method but it gives me 'first use in function'. I know I'm making a silly mistake but experts could figure it out easily. RootViewController.h #import <UIKit/UIKit.h> #import "ContentViewController.h" @interface RootViewController : UITableViewController { ContentViewController *contentViewController; } @property (nonatomic, retain) ContentViewController *contentViewController; - (NSString*)getContentFileName:(NSString*)title; //<--- This function declartion @end RootViewController.m #import "RootViewController.h" #import "HAWATAppDelegate.h" #import "ContentViewController.h" @implementation RootViewController @synthesize contentViewController; ... more methods ... #pragma mark - #pragma mark Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { HAWATAppDelegate *appDelegate = (HAWATAppDelegate *)[[UIApplication sharedApplication] delegate]; NSString *title = (NSString *) [appDelegate.titles objectAtIndex:indexPath.row]; NSString *fileName = getContentFileName:title; //<--- Here is the error ... } - (NSString*) getContentFileName:(NSString*)title { return [title lowercaseString]; } @end There must be a simple thing I'm missing. Please let me know. Thanks in advance.

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• Big time Leaking in Objective-C Category

  - by Daniel Amitay

  I created a custom NSString Category which lets me find all strings between two other strings. I'm now running into the problem of finding that there are a lot of kBs leaking from my script. Please see code below: #import "MyStringBetween.h" @implementation NSString (MyStringBetween) -(NSArray *)mystringBetween:(NSString *)aString and:(NSString *)bString; { NSAutoreleasePool *autoreleasepool = [[NSAutoreleasePool alloc] init]; NSArray *firstlist = [self componentsSeparatedByString:bString]; NSMutableArray *finalArray = [[NSMutableArray alloc] init]; for (int y = 0; y < firstlist.count - 1 ; y++) { NSString *firstObject = [firstlist objectAtIndex:y]; NSMutableArray *secondlist = [firstObject componentsSeparatedByString:aString]; if(secondlist.count > 1){ [finalArray addObject:[secondlist objectAtIndex:secondlist.count - 1]]; } } [autoreleasepool release]; return finalArray; } @end I admit that I'm not super good at releasing objects, but I had believed that the NSAutoreleasePool handled things for me. The line that is leaking: NSMutableArray *secondlist = [firstObject componentsSeparatedByString:aString]; Manually releasing secondlist raises an exception. Thanks in advance!

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• How can I split abstract testcases in JUnit?

  - by Willi Schönborn

  I have an abstract testcase "AbstractATest" for an interface "A". It has several test methods (@Test) and one abstract method: protected abstract A unit(); which provides the unit under testing. No i have multiple implementations of "A", e.g. "DefaultA", "ConcurrentA", etc. My problem: The testcase is huge (~1500 loc) and it's growing. So i wanted to split it into multiple testcases. How can organize/structure this in Junit 4 without the need to have a concrete testcase for every implementation and abstract testcase. I want e.g. "AInitializeTest", "AExectueTest" and "AStopTest". Each being abstract and containing multiple tests. But for my concrete "ConcurrentA", i only want to have one concrete testcase "ConcurrentATest". I hope my "problem" is clear. EDIT Looks like my description was not that clear. Is it possible to pass a reference to a test? I know parameterized tests, but these require static methods, which is not applicable to my setup. Subclasses of an abstract testcase decide about the parameter.

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• Implementations details of drag and drop of file path in cocoa.

  - by foo

  Hi, I'm trying to get a part of my window to react to drag and drop. In this case to copy the file path to the file being dropped on the view. I have looked over some documentation but I still have some problems to see exactly where I should implement my methods for drag and drop. I have seen some examples but almost all of them assumes that I want to drop an image on the view. I'm pretty new to cocoa and Xcode so, I have some problems with seeing the exact relation between interface builder and the generated code. I have created a subclass to NSView, called drop zone like this: #import <Cocoa/Cocoa.h> @interface dropZone : NSView { } @end I then use an NSRect to color it grey like this: #import "dropZone.h" @implementation dropZone - (void)drawRect:(NSRect)rect { NSRect bounds = [self bounds]; [[NSColor grayColor] set]; [NSBezierPath fillRect:bounds]; } @end I then drag this class to my window in interface builder. But I will need to implement the registerForDraggingTypes method, but where? I have also seen a convenience method in the Apple docs for file paths like this: dragFile:fromRect:slideBack:event: that might work.

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• .NET: bool vs enum as a method parameter

  - by Julien Lebosquain

  Each time I'm writing a method that takes a boolean parameter representing an option, I find myself thinking: "should I replace this by an enum which would make reading the method calls much easier?". Consider the following with an object that takes a parameter telling whether the implementation should use its thread-safe version or not (I'm not asking here if this way of doing this is good design or not, only the use of the boolean): public void CreateSomeObject(bool makeThreadSafe); CreateSomeObject(true); When the call is next to the declaration the purpose of the parameter seems of course obvious. When it's in some third party library you barely know, it's harder to immediately see what the code does, compared to: public enum CreationOptions { None, MakeThreadSafe } public void CreateSomeObject(CreationOptions options); CreateSomeObject(CreationOptions.MakeThreadSafe); which describes the intent far better. Things get worse when there's two boolean parameters representing options. See what happened to ObjectContext.SaveChanges(bool) between Framework 3.5 and 4.0. It has been obsoleted because a second option has been introduced and the whole thing has been converted to an enum. While it seems obvious to use an enumeration when there's three elements or more, what's your opinion and experiences about using an enum instead a boolean in these specific cases?

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• whether rand_r is real thread safe?

  - by terry

  Well, rand_r function is supposed to be a thread safe function. However, by its implementation, I cannot believe it could make itself not change by other threads. Suppose that two threads will invoke rand_r in the same time with the same variable seed. So read-write race will occur. The code rand_r implemented by glibc is listed below. Anybody knows why rand_r is called thread safe? int rand_r (unsigned int *seed) { unsigned int next = *seed; int result; next *= 1103515245; next += 12345; result = (unsigned int) (next / 65536) % 2048; next *= 1103515245; next += 12345; result <<= 10; result ^= (unsigned int) (next / 65536) % 1024; next *= 1103515245; next += 12345; result <<= 10; result ^= (unsigned int) (next / 65536) % 1024; *seed = next; return result; }

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• Refactoring. Your way to reduce code complexity of big class with big methods

  - by Andrew Florko

  I have a legacy class that is rahter complex to maintain: class OldClass { method1(arg1, arg2) { ... 200 lines of code ... } method2(arg1) { ... 200 lines of code ... } ... method20(arg1, arg2, arg3) { ... 200 lines of code ... } } methods are huge, unstructured and repetitive (developer loved copy/paste aprroach). I want to split each method into 3-5 small functions, whith one pulic method and several helpers. What will you suggest? Several ideas come to my mind: Add several private helper methods to each method and join them in #region (straight-forward refactoring) Use Command pattern (one command class per OldClass method in a separate file). Create helper static class per method with one public method & several private helper methods. OldClass methods delegate implementation to appropriate static class (very similiar to commands). ? Thank you in advance!

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• Using a Data Management Singleton

  - by Dan Ray

  Here's my singleton code (pretty much boilerplate): @interface DataManager : NSObject { NSMutableArray *eventList; } @property (nonatomic, retain) NSMutableArray *eventList; +(DataManager*)sharedDataManager; @end And then the .m: #import "DataManager.h" static DataManager *singletonDataManager = nil; @implementation DataManager @synthesize eventList; +(DataManager*)sharedDataManager { @synchronized(self) { if (!singletonDataManager) { singletonDataManager = [[DataManager alloc] init]; } } NSLog(@"Pulling a copy of shared manager."); return singletonDataManager; } So then in my AppDelegate, I load some stuff before launching my first view: NSMutableArray *eventList = [DataManager sharedDataManager].eventList; .... NSLog(@"Adding event %@ to eventList", event.title); [eventList addObject:event]; NSLog(@"eventList now has %d members", [eventList count]); [event release]; As you can see, I've peppered the code with NSLog love notes to myself. The output to the Log reads like: 2010-05-10 09:08:53.355 MyApp[2037:207] Adding event Woofstock Music Festival to eventList 2010-05-10 09:08:53.355 MyApp[2037:207] eventList now has 0 members 2010-05-10 09:08:53.411 MyApp[2037:207] Adding event Test Event for Staging to eventList 2010-05-10 09:08:53.411 MyApp[2037:207] eventList now has 0 members 2010-05-10 09:08:53.467 MyApp[2037:207] Adding event Montgomery Event to eventList 2010-05-10 09:08:53.467 MyApp[2037:207] eventList now has 0 members 2010-05-10 09:08:53.524 MyApp[2037:207] Adding event Alamance County Event For June to eventList 2010-05-10 09:08:53.524 MyApp[2037:207] eventList now has 0 members ... What gives? I have no errors getting to my eventList NSMutableArray. But I addObject: fails silently?

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